It is known for vehicles, such as automobiles and aircraft, to include an electronic display providing an image of, for example, an instrument cluster for replacing discrete mechanical or electrical dials. However, such displays are generally aesthetically limited because of their inability to produce images that differ from the standard two dimensional (2D) images displayed in the plane of the display. In addition to reducing the aesthetics of such displays, the inability to produce images that do not appear flat may provide limited realism of such displays. Although stereoscopic and autostereoscopic displays are known and can produce an impression of a three-dimensional image, such displays may produce eye strain and headache problems because of a potential limited freedom of viewing position and focussing issues.
It is also known for advertising displays, for example large-area public displays in shopping centres and digital signage displays on motorways, to aim to catch maximum attention. Although such displays are becoming more and more common, they generally do not include any aesthetically appealing features, aside from their large size, that would make them stand out of the ordinary and facilitate their acceptance. Overcoming the inability of such displays to produce images different from standard flat 2D images displayed in the plane of the display may therefore contribute towards their widespread acceptance.
It is also known for amusement devices, for example Pachinko machines, to include an electronic display in the centre of its layout providing, for example, movies, animations or a digital slot machine. Although such amusement devices show more and more attractive features with mechanical moving parts and abundant flashing lights, they are generally limited to a display which is unable to produce appealing images that differ from standard flat 2D images displayed in the plane of the display. Overcoming this issue by also making the display stand out of the ordinary may therefore contribute to increase enthusiasm and entertainment of players.
A first general class of prior art teaches how to make stereoscopic and auto-stereoscopic displays from a single panel. For example, FIG. 1 of the accompanying drawings illustrates a switchable 2D/3D (two dimensional/three dimensional) display based on the use of a parallax barrier, as disclosed in EP0829744 (18 Mar. 1998, MOSELEY Richard Robert; WOODGATE Graham John; JACOBS Adrian; HARROLD Jonathan; EZRA David). The parallax barrier comprises a polarisation-modifying layer 100, with alternating aperture regions 101 and barrier regions 102, and a polariser in the form of a polarisation sheet 103 which may be disabled. The parallax element provides the possibility of operating the display in a wide view full resolution 2D-mode or in a directional 3D autostereoscopic mode. However, this device produces a stereo image pair to generate 3D images rather than images with curved-appearance. Drawbacks of auto-stereoscopic displays include limited head freedom and inconsistency between 3D perception from stereo and from other cues (head motion, focus), leading to user confusion and sometimes eye strain and headaches.
A second general class of prior art is related to curved or conformal displays. For example, FIG. 2 of the accompanying drawings shows a display of the type disclosed in WO94/11779 (26 May 1994, GROSS Hyman Abraham Moses; ARTLEY Richard John; CLARK Michael George; HAYTHORNTHWAITE Arthur; WILKINSON Peter; WALLIS Miles). A curved liquid crystal display is manufactured by sandwiching a liquid crystal layer 104 between two curved pre-shaped transparent plastic substrates 105 or between two flexible substrates.
As illustrated in FIG. 3 of the accompanying drawings, US2006/0098153A1 (11 May 2006, SLIKKERVEER Peter J; BOUTEN Petrus Cornelis P; CIRKEL Peter A) discloses a display of the same type but where a curved display is formed by manufacturing a flat panel display layer 106 and thereafter curving the display layer itself by adhering an additional film 107 to it. The additional film may for example have been pre-stretched and the contraction force it releases after adhesion to the display results in the bending of the display.
Like flexible displays, although these curved displays are able to generate curved images, they all rely on displays which have been physically bent in order to produce the desired curvature. Such curved displays have many disadvantages, such as very high cost, limitations in material efficiency and material diversity, and strong difficulty in manufacturing. Further, displays of this type are very limited in their design as the variety of feasible curved-shapes is limited and, once a display has been manufactured with a specific curvature, this cannot be changed. Also, curved displays are not ready for mass-production yet as each production line would need to adapt to a particular curved design.
A third class of prior art concerns displays using projection onto curved surfaces. For example, U.S. Pat. No. 6,727,971 (27 Apr. 2004, LUCAS Walter A) and U.S. Pat. No. 6,906,860 (14 Jun. 2005, STARKWEATHER Gary K), disclose a display of the type illustrated in FIGS. 4a and 4b, respectively, of the accompanying drawings. In both cases, the display comprises at least one projector 108 and a curved screen 109, onto which is projected an image.
Such displays are well-known from the public area and are used for many applications such as the reconfigurable display from Digital Dash or immersive displays. However, they have the disadvantage of requiring a large space and being limited to projection technology only. Also, they are generally defined as constituting a display when considering together the projection system associated with the curved screen and not the projection system by itself.
A final class of prior art is related to head-mounted display applications. Displays for such applications usually use an optical system carefully designed to focus light from a display into the retina of an observer by means of as compact a device as possible.
For example, FIG. 5 of the accompanying drawings illustrates a display used for a head-mounted display, as disclosed in U.S. Pat. No. 6,304,303 (16 Oct. 2001, YAMANAKA Atsushi). The display uses folded optical path technology with two reflective surfaces 110 and 111 in order to reduce size and weight of the display and widen its angle of visibility. However, such a display aims to provide a high-quality image without curvature.
As shown in FIG. 6 of the accompanying drawings, U.S. Pat. No. 5,515,122 (7 May 1996, MORISHIMA Hideki; MATSUMURA Susumu; TANIGUCHI Naosato; YOSHINAGA Yoko; KOBAYASHI Shin; SUDO Toshiyuki; KANEKO Tadashi; NANBA Norihiro; AKIYAMA Takeshi) discloses a display of the same type but where, by use of a very different technology based on a lens system 112 combined with reflective layers 113 and 114, a virtual curved image 115 is generated in order to enhance presence and realism of the image to the observer.
GB2437553 (31 Oct. 2007, EVANS Allan; CURD Alistair Paul; WYNNE-POWELL Thomas Matthew) discloses a family of dual- and multiple-depth displays where a multiple-depth image is generated from a single display panel. Optical elements are placed a short distance in front of a display panel to produce differing depth effects from different optical paths. By use of polarisation effects and partial reflections, different images are associated with light paths of different lengths and appear to originate from different planes. By displaying these images time-sequentially or spatially-interlaced, a multiple-depth effect is achieved.
An embodiment from GB2437553 is shown in FIGS. 7a and 7b of the accompanying drawings. First and second partial reflectors 115 and 116 are placed in front of a liquid crystal display (LCD) panel 114 with polarisation-modifying optics 117 disposed between the first and second partial reflectors 115 and 116. The first and second partial reflectors 115 and 116 are separated from each other by an appropriate spacing for producing a depth-shifted image. Light from two different images displayed by the LCD panel 114 travels along different light paths towards the viewer. Light encoding the first image passes directly by transmission through the optical system to the viewing region as shown in FIG. 7b, whereas light encoding the second image follows a folded optical path 118 before reaching the viewer as shown in FIG. 7a. As a result of the different lengths of the different paths 118 and 119, the first image appears at the location of the LCD 114, whereas the second image 120 of the LCD is shifted in depth so as to appear below the LCD. The viewer thus observes images in different depth planes.
Displays of this type have clear advantages over multiple-depth displays using multiple display panels, for example in terms of cost, brightness and volume. However, the main purpose of these displays is to create two or more images, separated in depth. In addition, the partial reflectors in the optical system of such displays are parallel to each other and to an image surface of the display.
When two images must be presented independently to a viewer from the same underlying display, there is some leakage or crosstalk between the views and this may be corrected by modifying the image data sent to the display. Crosstalk can be effectively removed, but there is also a loss of contrast.
EP0953962 (3 Nov. 1999, JONES Graham; HOLLIMAN Nicolas) discloses crosstalk correction in 3D and dual-view displays. For these two types of display, crosstalk tends to be symmetric and colour-independent. In other words, the leakage from image 1 to image 2 is the same as the leakage from image 2 to image 1, and also the same for red, green and blue components of the image.
GB2437553 discloses the same basic principle of crosstalk correction but applied to dual-depth displays. For this type of display, crosstalk tends to depend upon which plane leakage is originating from, as well as on colour.
GB2449682 (3 Dec. 2008, GAY Gregory; WALTON Harry Garth) describes an optical system for converting a standard flat image to a non-flat image. It uses a folded optical light path technology based on reflective layers 121, 122, at least one of which is curved, and an additional uniform switchable LC cell to provide electrical switching between a standard flat image mode and a non-flat image mode. An embodiment from GB2449682 is shown in FIGS. 8a and 8b of the accompanying drawings. When the additional switchable half-wave plate 123 is switched off, light passes directly by transmission through the optical system to the viewing region as illustrated in FIG. 8a. When the additional switchable half-wave plate 123 is switched on, light follows a doubly-reflected light path 124 as shown in FIG. 8b. Because of the doubly-reflected light path 124 and of the curved-shape given to the reflective polariser 122, the optical light path is longer towards the edge of the display and the display image is observed with a curved appearance 125.
Displays of this type can provide a non-flat image from a conventional flat display with the capacity of switching electrically between a standard 2D-mode and a curved-appearance mode. However, the additional LC cell required for the switching adds extra cost and deteriorates image quality of the display by increasing crosstalk in both image modes. In addition, because the reflective films are fixed in place, image curvature displayed in the curved-appearance mode has to be decided at the manufacturing step and will be fixed thereafter.